Pipes, such as gas conduits, sewers, water mains and culverts, periodically require replacement or rehabilitation due to leakage caused by cracks or deterioration. Such pipes may be steel, corrugated sheet metal, cement, concrete, or brick. Replacement or rehabilitation of such pipes, particularly underground pipes, has heretofore been cumbersome, in part, because often the pipe must be unearthed for removal. Underwater pipes are also traditionally difficult to rehabilitate, given specialized equipment and workers must be employed. Rehabilitation of pipes running through protected wetland areas present additional difficulties, because leakage from damaged pipes, or leakage during a repair operation, may have deleterious environmental consequences.
A relatively short section of pipe, such as a few feet or less, having a relatively small diameter, such as 12 inches, may be easily replaced. However, often times a damaged pipe may not be easily reached for replacement. In addition, it may be difficult to remove a section of pipe, given the fluid in the pipe must be completely stopped from flowing during the entire replacement process. Furthermore, replacement techniques may not be viable for long sections of pipe or pipe having a relatively large diameter, such as 12 feet or more. Replacement may also be an impractical or overly expensive in some situations, such as replacing a culvert under a busy highway, wherein traffic would have to be stopped or rerouted for an unacceptable period of time.
Some methods have been developed which facilitate the replacement of underground pipe without the need to unearth the entire length of damaged pipe. Some methods involve digging trenches on opposite sides of a section of pipe to be replaced. A tensioned guide cable attached at one end is passed through the section of pipe being replaced. The cable is also attached to a winch. The pipe is fragmented, with the fragments pushed into the surrounding earth, and a new flexible pipe is pulled into place. This process is sometimes referred to as “pipe bursting.” Pipe bursting eliminates the need to completely dig up the old pipe to replace it. However, it may not be viable or practical to dig trenches for the same reasons noted above.
Other methods provide for a soft liner that is fed into a pipe to be repaired, sometimes referred to as “soft lining.” Generally, a tubular liner is constructed to have a soft and flexible character so that the liner can be moved into the pipe. By fluid pressure, the liner is urged against the pipe surface being lined. The liner shapes to the surface contour and bonds to the pipe surface.
Methods of rehabilitating manholes are disclosed in U.S. Pat. Nos. 6,368,025; 5,915,886; and 5,265,981, the disclosures of which are all incorporated herein by reference and the invention of which is the inventor hereof. A method and apparatus for inflating and curing such a resin impregnated manhole liner is disclosed in U.S. Pat. No. 5,490,744, the disclosure of which is incorporated herein by reference and is also the invention of which is the inventor hereof. In my referenced patents, the resin-impregnated outer fiberglass layer bonds to the manhole. However, such an installation is not feasible with underground pipes due to their length and the possibility of water.
Although the methods of rehabilitating sewers disclosed in the above referenced patents provide some advantages over prior methods, they do not disclose a practical method of reinforcing a pipe that is relatively long, such as 100 feet or more.